24-01-2013, 12:02 PM
Compressive Strength of Volcanic Ash/Ordinary Portland Cement Laterized Concrete
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Abstract:
This study investigates the effect of partial replacement of cement with volcanic ash
(VA) on the compressive strength of laterized concrete. A total of 192 cubes of 150mm
dimensions were cast and cured in water for 7, 14, 21, and 28 days of hydration with cement
replacement by VA and sand replacement by laterite both ranging from 0 to 30% respectively,
while a control mix of 28-day target strength of 25 N/mm2 was adopted. The results show that
the density and compressive strength of concrete decreased with increase in volcanic ash content.
The 28-day, density dropped from 2390 kg/m3 to 2285 kg/m3 (i.e. 4.4% loss) and the compressive
strength from 25.08 N/mm2 to 17.98 N/mm2 (i.e. 28% loss) for 0-30% variation of VA content
with no laterite introduced. The compressive strength also decreased with increase in laterite
content; the strength of the laterized concrete however increases as the curing age progresses.
Introduction
Research trends globally in materials development
has been that of sourcing for alternatives necessitated
by the high cost of conventional materials, difficulty
in accessing fund for construction/building development,
the need to recycle agricultural waste
materials for construction, the bio-degradability of
the materials, the need to maintain ecological
balance and population growth and the challenges of
housing amongst the many other reasons [1,2,3,4].
The development of supplementary cementitious
materials (SCMs) is said to be fundamental to
advancing low-cost construction materials to be used
in the production of self-sufficient means of shelter
especially in developing countries. Apart from
improving concrete properties, the main benefits of
SCMs include saving natural resources and energy
as well as protecting the environment through the
use of these main admixtures [5].
Materials and Methods
Laterized concrete mixtures with four levels of
volcanic ash (VA.) replacements ranging from 0 to
30% and four levels of laterite replacement also
ranging from 0 to 30% (i.e. a total of 16 levels of
samples produced in triplicates) were investigated.
The control mixture was proportioned for a target
concrete strength of 25 N/mm2 and had a
cementitious material content of 292 kg/m3, fine
aggregate content of 680 kg/m3, coarse aggregate
content of 1158 kg/m3, and a water cementitious
materials ratio of 0.65 giving a free water content of
190 kg/m3. The cement and sand replacement by VA
and laterite respectively was thereby computed for
by weight as required.
The volcanic ash used was obtained from Kerang in
Mangu Local Government Area of Plateau State in
Nigeria as a solid mass. This was grinded and sieved
with a 75 μm sieve at the Civil Engineering
Laboratory of the Federal University of Technology,
Minna, Nigeria. As shown in Table 1, the total
content of Silicon Dioxide (SiO2), Aluminium Oxide
(Al2O3) and Iron Oxide (Fe2O3) can be said to range
between 63.74% reported by Lar and Tsalha [29] and
67.14% by Hassan [23], which is slightly below the
minimum of 70% specified in ASTM C618 [20].
Results and Discussion
Workability of the laterized concrete decreases as the
percentage of VA and laterite (lat) increases. The
slump value ranges between 40-60 mm. The density
of the laterized concrete mixtures decreases as the
percentage VA replacement increases, so also as the
lat content increases. At 0% VA / 0% lat, the density
was 2390 kg/m3; at 30% VA / 0% lat, the density was
2285 kg/m3 representing decrease of about 4.4%
(Tables 3 and 4).
Conclusion
The results presented demonstrate that although
the VA/OPC laterized concrete only had compressive
strength values ranging between 48% and 73% of
the 28-day strength (for 30% lat / 30% to 0% VA), the
introduction of volcanic ash (VA.) presents a good
tendency of pozzolanic activity, while research
studies towards boosting the property of the volcanic
ash sample from the study area will be a welcome
development in the continued search for
alternatives. The VA/OPC laterized concrete can at
the moment be adopted for construction of masonry
walls and simple foundations.